Bicyclomycin, a new antibiotic. IV. Absorption, excretion and tissue distribution.

Bicyclomycin, a new antibiotic active against Gram-negative bacteria and having a unique chemical structure, was investigated for its absorption, excretion and tissue distribution. Bicyclomycin was intramuscularly administered to mice, rats, rabbits and dogs at a single dose of 50mg/kg. Although the mean peak levels in the blood and serum differed with animal species, the values were found to be fairly high. Seventy % or more of the given dose were recovered in the 24-hour urine samples. A relatively long half-life of bicyclomycin was observed as compared with that of ampicillin, when both antibiotics were administered intravenously to rabbits at a single dose of 50mg/kg. The results of the study on the biliary excretion in rats showed its low excretion rate after a single intramuscular dose of 50mg/kg. When a single intramuscular dose of 100mg/kg was given to rats, bicyclomycin was well distributed in various tissues, and the highest concentration was observed in thekidney. In human volunteers, mean peak serum levels were 18.0 and 31.9 mcg/ml at the first 30minutes and 1hour when dosed intramuscularly at 500mg and 1 g, respectively. Urinary excretions of bicyclomycin were relatively high, i.e. 96.2 and 94.8% at a dose of 500mg and 1g, respectively, during 24hours.